In the manufacture of note pads, drawing pads, or similar materials, it is common in forming the pad to accumulate paper sheets in a stack and periodically insert paper boards into the stack. The paper boards serve as backing to each pad from the stack. Each backing board can then be cemented at one edge to the sheets above it to produce each pad.
Typically, paper sheets are added to the stack one at a time as they exit a printing press or after they are delivered and cut from a web. The backing boards are typically added either as the individual sheets fall onto the stack, or as the sheets are transported to the stack on a conveyor system.
For example, Pulskamp U.S. Pat. No. 4,624,452, the inventor herein, describes a mechanism that periodically injects paper boards onto a stack of paper sheets as the sheets fall one at a time from a printing press onto the stack. Broadmeyer U.S. Pat. No. 1,709,004 and Munn U.S. Pat. No. 3,979,112 disclose mechanisms which periodically add paper boards, or like material, onto a conveyor which is used to transport individual paper sheets in an end-to-end fashion. The sheets and boards are ultimately deposited on a stack thus producing a pile of paper sheets with backing boards interleaved at predetermined intervals. While these apparatus are fairly effective for the applications disclosed, they are limited by the fact that the paper sheets are transported along a conveyor in an end-to-end fashion or otherwise delivered to the stack one at a time.
Often, instead of being configured end-to-end, paper sheets are transported on a conveyor system in a shingled or overlapping manner. This particular configuration renders the above referenced art inadequate as merely placing a board on the stream of papers will fail to integrate that board into the paper stack. Instead, the paper boards must somehow be shuffled into the stream of shingled sheets, or alternatively, the stream of sheets must be interrupted to allow the addition of the board into the stream.
Faeber U.S. Pat. No. 3,149,834 discloses a method for interrupting a stream of sheets moving along a conveyor. In this method, the stream is "pinched" at a particular point so that certain sheets within the stream are held in place while allowing the sheets immediately in front of the pinched sheets to continue moving along the conveyor system. This in turn creates a gap in the stream after the pinched sheets are released. Although not disclosed in the Faeber patent, cardboard backing material could be added to the paper stream at this point for later deposit into a stack. A drawback to this particular method is that paper sheets bunch up behind the pinched portion of the stream increasing the likelihood of a jam or similar problem.
Additionally, these conventional methods require mechanisms that are typically dedicated to whatever conveyor system is already in use. These mechanisms, even standing alone, can be expensive. To the extent that the above referenced methods can be added as attachments to an existing conveyor system, complicated and expensive adaptations may be required.